Methodology
Most online "calculators" are lead traps with made-up numbers. Here's exactly what ours does — every input, every factor, and what it can't do.
The formula
Roof surface area = home footprint × pitch geometry factor × waste allowance (10–20% by complexity).
Base cost = roof surface area × material cost per sq ft (low–high range, 2026 installed pricing).
Final range = base × regional multiplier × pitch labor factor × complexity factor × stories factor × tear-off/overlay factor.
Material costs (per sq ft, installed, 2026)
| Material | Low | High | Typical lifespan |
|---|---|---|---|
| Architectural asphalt shingle | $4.25 | $7.25 | 25–30 yrs |
| Standing seam metal | $10.00 | $16.00 | 40–70 yrs |
| Clay / concrete tile | $11.00 | $18.00 | 50–100 yrs |
| Natural slate | $18.00 | $35.00 | 75–150 yrs |
| Wood shake | $8.50 | $14.00 | 25–40 yrs |
Sources: 2026 contractor pricing guides (full list in our data notes). Note that 50%+ steel and aluminum tariffs pushed metal roofing to record highs in 2026 — don't trust pre-2025 quotes.
Regional adjustment
Your ZIP maps to a state, and states fall into five cost tiers (0.90× in the lowest-cost states up to 1.35× in premium markets like California and New York), based on published regional labor-rate data. Labor is 60–70% of a roof job, so location genuinely swings the total 20–40%.
Pitch, complexity, stories
- Pitch changes both surface area (geometry) and labor: steep roofs (8/12+) carry a documented 25–50% labor premium for safety rigging and slower work.
- Complexity adds cutting, flashing, and waste: complex roofs run 25–40%+ above simple ones.
- Stories add access cost: two-story +5%, three-story +10%.
- Tear-off vs. overlay: overlay saves roughly 15% (~$1,000–$3,000 on typical jobs) but hides the deck — we only allow it for asphalt, since that's the only material where it's common practice.
What this estimate can't do
- See rotted decking ($80–$120 per sheet to replace), which is only found after tear-off.
- Price permits ($100–$500), skylights, chimneys, or HOA/historic-district rules.
- Account for your insurance coverage — storm damage may be covered beyond your deductible.
- Predict 2026 tariff volatility beyond what's already in the base data.
An identical 25-square asphalt reroof can legitimately quote at $9,500 in one market and $22,000 in another. Always get at least three local quotes — that's the single highest-value step in this whole process.